1. Technical Field
The present disclosure relates to a resin for use in toner, a toner using the resin, a developer using the toner, image forming apparatus and method using the toner, and a method of manufacturing resin.
2. Description of Related Art
In an electrophotographic image forming apparatus or electrostatic recording device, an electric or magnetic latent image is developed into a toner image. In electrophotography, for example, an electrostatic latent image is formed on a photoreceptor and is developed into a toner image. The toner image is transferred onto a recording medium, such as paper, and fixed thereon by application of heat, etc.
Toner generally comprises resin particles in which colorant, charge controlling agent, etc., are dispersed, and is manufactured by various processes, such as pulverization, suspension polymerization, dissolution suspension, emulsion aggregation, phase-transfer emulsification, and elongation polymerization.
The resin particles may comprise, for example, a thermoplastic resin such as styrene-acrylic resin, polyester resin, and polyol resin. Polyester resin has superior strength and stability as well as a lower softening point while having a greater molecular weight and a higher glass transition temperature compared to styrene-acrylic resin. Therefore, polyester resin is widely used for toner especially requiring low-temperature fixability. In particular, polyester resin is widely used for toner for full-color printing.
Binder resin generally occupies 70% or more of toner composition. Most binder resins are derived from petroleum resources now being exposed to depletion. Petroleum resources cause a problem of global warming because they discharge carbon dioxide into the air when consumed. On the other hand, binder resins derived from plant resources have been proposed and used for toners. Because plant resources have incorporated carbon dioxide from the air in the process of growing, carbon dioxide discharged from plant resources is merely circulated between the air and plant resources. Thus, plant resources have the potential to solve the problems of both depletion and global warming. For example, polylactic acid, which is readily available, has been used for toner binder.
Polylactic acids consisting of L-form or D-form have high crystallinity. Such polylactic acids are poorly soluble in organic solvents, and therefore they cannot be used for toners manufactured through a process in which binder resin is dissolved in organic solvents. Therefore, polylactic acids are applied to pulverization process, but the pulverization processes undesirably waste a large amount of toner particles in the classification process.
Japanese Patent Application Publication No. 2008-262179 proposes to mix L-form and D-form polylactic acids to reduce crystallinity. It is disclosed therein that solubility in organic solvents is improved thereby.
Japanese Patent Application Publication No. 08-302003 describes a copolymerized polylactic acid obtained by reacting lactic acid with a reaction product of an aromatic dicarboxylic acid with an aliphatic diol, having a low glass transition temperature of 60° C. or less. Japanese Patent Application Publication No. 2007-112849 describes a copolymerized polylactic acid having a fluorenone skeleton, having a glass transition temperature of 60° C. or more.
In attempting to improve low-temperature fixability, Japanese Patent Nos. 4307367 and 3778955 each propose to introduce a soft segment into binder resin.